Blue diamond not eating, dark patch on nose, mucusy poop

Problem

1. Please explain the problems with your fish. When did you notice the problems and did anything unusual happen that you think started them? Just ended treatment of Prazipro for 7 days (all 4 had tapeworms) and it's now day 14. In those 7 days the Prazi caused white slimy algae to build up in the tank glass (cleaned and scraped it everyday to keep it at bay) they no longer show signs of tapeworms but on day 7 the blue diamond stopped eating and has a brown/dark patch from the top of its mouth to the start of what I guess would be the forehead. All other fish are fine and literally just witnessed my Ring Leopard lay eggs all over my heater just to watch my red melon eat them all up lol.

2. Symptoms (i.e. turning dark, excess slime, not eating, clamped fins, flashing, darting, clamped gills, white/yellow/green poop, hiding, headstanding or tailstanding, white on tips of fins, rotting or fungus, blisters/white zits on fish, bloated, cloudy eyes, wounds).
Not eating, turning dark on nose, occasionally flashes too dorsal fins, white mucusy poop

3. What medications/ treatments have you already tried and what were the results. Include dosage and duration of treatment.
Just finish Prazipro for another issue of what I believe we're definitely tapeworms

Tank/Water

4. Tank size and ages, numbers and sizes of fish.
55 gallon, 6 months old. 4 discus 2.8? Red turquoise? 3in blue diamond, 3.5 red melon, 5in Ring Leopard. 12 cardinal tetra, 3 sterbai Cory cat.

5. Water change regime (What percentage and how often).
I drain about 35 to 40 gallons every day.

6. How long has tank been running? Is it bare bottom? If you have substrate, what type and how deep is it?
Running about 6 months. Bare bottom for about 3 weeks

7. Do you age your water? If you do for how long and what is the ph swing.
Age 30 gallons of water for 24 hours, pH goes from around 7.4 to 6.8. if more water needs to go into the tank I fill the rest with tap water that runs through 5 polishing pads to remove micro bubbles cause why not

8. Parameters and water source;

Note: Water Parameters are important in diagnosing problems within a tank. If you don't own test kits for the following information, you can purchase them, test your parameters and post this info as soon as possible.

- temp ___85.8-86.3__

- ph ____6.8_

- ammonia reading ____0

- nitrite reading ____0

- nitrate reading ____5-10

What type of water or combinations of water sources do you use? If it is an RO/tap/well water mix, please list percentages in the mix.

- well water ____

- municipal water ____100%

- RO water ____

9. Any new fish, plants or inverts added recently.
Just the discus

10. Please tell us what you feed your fish and how often. This can be critical information for solving the problem so be as specific as you can.
Feed in order of frozen shrimp, omega1 color flakes, frozen bloodworms, Hans discus flakes, and frozen spirulina brine shrimp.

11. Include any pictures or videos you have which shows the symptoms. If you can't add them to this post, please provide a link to them.

Attachment 115138 Attachment 115139 Attachment 115140

And here's what my Ring Leopard was upto this morningAttachment 115141

And this is the link to the thread I had when I experienced the tapeworms and algae (thanks for that help Pat)http://forum.simplydiscus.com/showth...75#post1286175